Sure it is difficult to do and yes it has been simplified.
Why not try based on your limited information?
I rarely mind answering direct questions as I'm an opinionated bastard, although I'm much more likely to if the one I'm conversing with shows a willingness to answer questions too. So before I go down your list of 5 questions I will reiterate the first question about Schneiderlin I've asked you: You're the one saying that Schneiderlin was Southampton's 5th or 6th best player, would you mind answering how much you've seen of them and him this season to form that opinion?
a) This is pure speculation, but somewhere above £15m and below £30m with a fee somewhere around Lovren's looking quite likely to me.
b) As I've already said the equivalent player from outside the PL isn't a great comparison for me. I've long been saying in several threads that I think we should focus on players with PL experience this summer after signing 7 players without PL experience last season as we look to integrate them and the rest of our team under a new manager. Given this I certainly wouldn't be unhappy if we signed him for £20m and would be happy with £25m too, £30m and above is my pain threshold.
c) I rate Bentaleb higher than most, but he's clearly still young and inexperienced and I'm not convinced he's ready to be our first choice throughout a long season. For Sandro, Paulinho, Dembele and Capoue it might very well be that Schneiderlin isn't objectively "better" than the best two out of those four. But he's a different type of player and a player type we've been missing for some time now. Based on what I've seen (my limited information) I expect him to be a significantly better passer, pass and move player and deep playmaker type than any of those 4. I don't consider Chadli an option for that role at this point. Having a balanced squad is at least as important as the objective quality of one player compared to another of a different type. This is where Sherwood was right about our midfield being "a bit much of a muchness".
d) Probably not much more than £30m as he's a non goalscoring central midfielder and that's in the ballpark of what they've been willing to pay for Alonso and Modric for example. At 24 (soon 25) he's unlikely to rise significantly in value.
e) a) The chances of him only getting 10 appearances are very small unless he picks up a string of serious injuries, knock on wood and all that. b) This seems to me clearly possible, but not the most likely outcome, but this depends a lot on your definition of average. c) Fairly unlikely. d) The chances of him being a success and staying with the club for more than 2-3 seasons is significant.